In Harrington on Hold'em II, Dan Harrington introduces the theory of M, which is a ratio of your stack size compared to the blinds and antes. The 'M' value calculated will guide you how you play certain hands for the remainder of the poker tournament.
Calculating Harrington's M Value
Calculating your M value is relatively simple, but it does rely on their being a full table of 9-10 players. All you do is calculate how much a full dealer rotation will cost you in terms of blinds and Antes by adding (If there are no antes then this is easy to do, it's simply the small blind + big blind). You then divide your stack size by the by this number and this will give you your 'M' Value. For example if you have 3000 chips and the total blinds are equal to 600 then your 'M' is 5.
Why is an M Value useful?
By knowing your M score during a tournament you use it to adjust your strategy accordingly and play in Dan Harrington's theoretical "Poker Zones". The M Level and the M value of your opponents determines which 'zone' you play in. There are 5 zones in total, the higher you value of M, the more freedom you have to play.
Green Zone (M = + 20)
All your basic play is available to you.
Yellow Zone (M = 10 to 20)
Small pairs and suited connectors are less useful as you are no longer getting good implied odds (chance of winning a huge pot from a small outlay).
Orange Zone (M = 6-10)
You have lost the ability to "resteal", you have be picking up the blinds of the weaker players while avoiding the big stacks.
Red Zone (M = 2-6)
Here you almost have no option but to go "all in" and fold. Make sure you're first to enter the pot to give your opponent some fold equity.
Dead Zone (M = 0-2)
Move all in with anything.
Try and avoid being in the dead zone at all costs, doubling up at this stage isn't really going to help you. You should try and find a spot much earlier.